It is well known in the printing industry that it is extremely difficult to obtain high quality when printing certain forms, such as one-half page, combinations of screens and solids, diagonals, and the like. These forms are difficult to print because of the problems associated with "ghosting", ink starvation and accumulation, linting, or ink slinging. Some of these problems have been partially solved by the inovative inventions disclosed in Pat. Nos. 4,208,963, 4,233,898, and 4,237,785.
In U.S. Pat. No. 3,926,114 to Matuschke and U.S. Pat. No. 3,587,463 to Granger, it has been suggested that a scraping off device be positioned to engage an inking roller in a letterpress to remove the negative ink relief to thus avoid the accumulation of ink on rollers in an ink supply mechanism. In letterpress printing, ink is applied to raised image areas on a printing cylinder while recessed nonimage areas remain free of ink. However, in lithographic printing, ink and dampening fluid are applied to a planographic printing plate. U.S. Pat. No. 3,926,114 to Matuschke discloses a device in which ink and dampening fluid scraped off of a roller are passed into a separator so that the characteristics of the ink are not altered by the add mixture of dampening fluid. Thus, pure ink was metered to the form roller by the inking system, to prevent "greying" or the accumulation of excess dampening fluid within the ink supply as the ink was transferred to the inking roller.
U.S. Pat. No. 4,211,167 to Corse discloses a rod pressed under strong pressure against a soft surface carrying a layer of ink and dampening fluid, the rod forming a barrier only against the dampening fluid while allowing all the residual film of ink remaining on the inking roller to pass and return to a mass of ink in a reservoir.
The present invention provides a solution to problems encountered in separating ink and dampening fluid by permitting the emulsified ink and dampening fluid to be used again. We have discovered that if unused ink and dampening fluid are thoroughly mixed with fresh ink to form a substantially homogeneous mixture, ink and dampening fluid removed from a lithographic printing press equipped with an inker and a dampener can be removed from a form roller to prevent accumulation and remetered for application to the form roller provided the emulsified ink and dampening fluid are not kept in a confined area long enough for the ink and dampening fluid to separate.
Accordingly, it is an object of the present invention to provide an ink removal, circulating and distributing system that meters a substantially homogeneous mixture of ink and dampening fluid to a form roller for use in a lithographic printing system wherein an improved distribution system maintains the homogeneous mixture sufficiently agitated to prevent separation of the ink and dampening fluid.
Further, it is an object of the present invention to provide a substantially homogeneous mixture of printing ink and dampening fluid for use in a printing system.
It is a further object of the invention to provide a circulating system which eliminates heat build up in an ink reservoir.
A further object of the invention is to maintain a uniform viscosity consistency of an ink emulsion throughout a printing run.
A still further object of the invention is to provide apparatus to remove ink and dampening fluid from a form roller and to reapply the ink and dampening fluid to the form roller, in combination with a dampener having a hydrophilic roller adapted to deliver a metered film of dampening fluid to the form roller and to remove excess dampening fluid from the form roller.